The family of materials known as zeolites constitute a large group of silicates having appreciable void volume within their structures. In the ideal state they may be viewed as built from corner shared SiO.sub.4.sup.4-- tetrahedral building units which form a large range of architectures comprising cavities, channels and cages. In the pure silica forms the structures are charge neutral frameworks stuffed with either neutral molecules, usually water or other neutral solvent molecules, or salt pairs, such as NaCl. These pure silica forms have been designated "clathrasils" or "zeosils" (Liebau et al., Zeolites, v.6, 373, 1986). More commonly Al substitutes for some of the silica, in which case the framework possesses a net negative charge which is balanced by "exchangeable" cations-commonly those of Groups 1 and 2 of the Periodic Table (Kirk-Othmer Encyclopedia of Chemical Technol., J. Wiley (New York), v.8, 94, 1965). However, numerous substitutions are now recognized as being possible both in the Si framework substituents and the exchangeable cations, as demonstrated in much of the recent art. A major expansion of these structural types has been achieved with the recognition that AIPO.sub.4 has many structures beyond the well known silica analogues of quartz-tridymite--cristobalite (Flanigen et al., Proc. 7th Intl. Zeolite. Conf., Ed. Murakami et al., Kodansha/Elsevier (Tokyo), p. 103, 1985). Many zeolites occur as minerals (Tschernich, "Minerals of the World", Geoscience Press (Phoenix, Ariz.) 1992), some of which have no synthetic counterparts. Similarly many synthetic zeolites have no naturally occurring counterparts. The large number of existing known structures has been reviewed by Meier and Olson ("Atlas of Zeolite Structures", Butterworths-Heinemann Press (London), 1992). The unique catalytic, sorption and ion-exchange properties of these zeolite "molecular sieves" have been utilized in many industrial and environmental processes, and numerous consumer products. (As reviewed in the periodic Proceedings of the International Zeolite Conferences).
There are a large number of synthetic methods for producing zeolites, well illustrated in the patent literature and reviewed by Barrer (in "Hydrothermal Chemistry of Zeolites", Academic Press (London), 1982), Breck (in "Molecular Sieve Zeolites", J. Wiley (New York), 1974) and Jacobs and Martens (in "Synthesis of High Silica Alumino-silicate Zeolites.", Elsevier (Amsterdam), 1987). Reactants may be general or specific and typical reaction conditions are below about 250.degree. C. and 50 bars pressure. The primary solvent is usually water, but others, such as ammonia (e.g., U.S. Pat. No. 4,717,560) and organic liquids (e.g., U.S. Pat. No. 5,160,500), have also been used. Methods for controlling the zeolite type produced, and its composition, include "seeds" as nucleation centers and organic molecules (frequently alkylammonium salts) as structural "templates".
In addition to the many known natural and synthetic zeolite structures built from corner shared tetrahedra, there are innumerable structures which are theoretically possible from the viewpoint of poyhedrageometry and mathematical combinatorial theory (e.g., Smith, Proc. 8th Intl. Zeolite Conf., Elsevier (Amsterdam), p. 29, 1989; Treacy et al., Proc. 9th Intl. Zeolite Conf., Butterworths-Heinemann (MA, USA), p. 381, 1993). The challenge of the synthetic chemist is to discover the synthesis methods that will make possible their creation.
This invention relates to a novel zeolite, ECR-31, and to a novel process for its preparation. In particular, the zeolite has a structure in which the main feature seems to be a one dimensional, 12-ring channel (FIG. 1). An unusual characteristic of its synthesis is that it is synthesized from a co-solvent system containing ammonia and water.
Several zeolites containing 12-ring channels are well known in the literature, such as mordenite, offretite, gmelinite, cancrinite, mazzite, ECR-1 and Linde L. Several of these have important catalytic properties which made them useful in such processes as isomerization (mordenite and mazzite), dewaxing (mordenite and offretite) and aromatization or reforming (Linde L). The specific unique properties are thought to be derived from combinations of structural features and chemical composition, often associated with particular noble metal dispersions. The differences in channel configuration in several of these materials has been illustrated by Gramlich-Meier and Meier (J. Solid State Chem., Vol. 44, p. 41 (1982)).
ECR-31 is a new zeolite structure with a unique channel configuration, an "as synthesized" SiO.sub.2 /Al.sub.2 O.sub.3 ratio between 3 and 10, and an estimated unit cell which is proposed to be hexagonal with approximate axes of a=18.5 .ANG. by c=7.6 .ANG.. Although two well known zeolites (Linde L and mazzite) and one well publicized theoretical structure (Omega of Barrer & Villiger) have such a unit call, ECR-31 has an x-ray diffraction pattern different from any of these. Compared to the LTL pattern, peaks representing 111, 221, 331, and 441 of LTL are missing. However, numerous other structures may have these cell dimensions (Treacy, et al., ibid). ECR-31 shows a strong absorption peak in the I.R. spectrum at 605 cm.sup.-1 and a shoulder at 1130 cm.sup.-1 (FIG. 2), previously associated with 6-rings and 5-rings, respectively, in zeolite structures (Flanagan, et al. Adv. Chem. Sec. 101, p. 201, (1971)).